First, the gate valve
Gate valves, also known as gate valves, are among the most commonly used types of valves in piping systems. They are designed to allow or stop the flow of a medium by lifting or lowering a gate that sits between two sealing surfaces. This mechanism provides a tight seal when closed and minimal resistance when fully open.
Working Principle: The gate is connected to a stem that moves vertically. When the stem is turned, it lifts the gate away from the seat, allowing fluid to pass through. When the gate is lowered, it blocks the flow completely. This makes them ideal for shut-off applications.
Advantages: Gate valves offer low fluid resistance, especially when fully open. They can handle bidirectional flow without direction restrictions. They are durable, suitable for both small and large pipelines, and provide excellent sealing when properly maintained.
Disadvantages: One major drawback is their relatively high profile, which requires more vertical space. They also take longer to open and close compared to other valves. Maintenance can be challenging, and manual operation becomes difficult for larger sizes.
Gate valves come in different types, such as rising stem (also called "through-stem") and non-rising stem (or "dark stem") designs. They can also be classified based on the gate structure—parallel or wedge-shaped—and whether they have a single or double gate.
Second, the globe valve
Globe valves are another common type of valve, typically used in smaller pipe diameters, usually below 100mm. Unlike gate valves, the closing element (the plug) moves along the centerline of the valve seat, creating a linear motion to control the flow.
Working Principle: The plug moves up and down, adjusting the size of the opening between the plug and the seat. This allows for precise flow regulation, making them useful for throttling applications as well as full shut-off.
Advantages: Globe valves are easy to manufacture and maintain. They are durable and offer good sealing performance under normal conditions.
Disadvantages: They are directional, meaning the flow must follow a specific path during installation. They also create higher flow resistance and may not seal as effectively as other valve types when partially closed.
Common types include straight-through, right-angle, direct current, and balanced designs. In engineering projects, flanged straight-through (J41H) and internally threaded straight-through (J11H) models are frequently used. These valves must be installed correctly, as reversing them can cause failure.
Third, the ball valve
Ball valves are a modern and widely adopted type of valve, known for their reliability and efficiency. Their design uses a spherical closure element with a bore that aligns with the pipeline when open and blocks the flow when rotated 90 degrees.
Working Principle: A stem connects to the ball, allowing it to rotate within the valve body. This simple mechanism provides quick and effective shut-off capabilities.
Advantages: Ball valves offer excellent sealing properties, often achieving zero leakage. They are compact, easy to operate, and suitable for a wide range of applications, including petrochemical, power, and aerospace industries.
Disadvantages: While efficient, they can be difficult to repair due to their internal components. There are two main types: floating ball and fixed ball, each suited for different pressure and temperature conditions.
Fourth, the butterfly valve
Butterfly valves are the most commonly used type in heating systems due to their simplicity and cost-effectiveness. They feature a disc that rotates around a central shaft to control the flow.
Working Principle: When the disc is aligned with the pipeline, the valve is open. Rotating it 90 degrees closes the valve. This allows for both shut-off and flow adjustment.
Advantages: Butterfly valves are lightweight, easy to install, and provide good sealing performance. They are ideal for large-diameter pipelines where space is limited.
Disadvantages: When fully open, the disc is exposed to the flowing media, which can cause wear over time.
In heating projects, three-eccentric metal-sealed and rubber-sealed butterfly valves are commonly used, depending on the system requirements.
Fifth, the check valve
Check valves, also known as non-return valves or one-way valves, are essential in preventing backflow in pipelines. They operate automatically based on the pressure of the fluid itself.
Working Principle: When the flow is in the correct direction, the valve opens. If the flow reverses, the valve closes, preventing damage caused by backflow. This is particularly important in pump systems to avoid water hammer effects.
Common types include horizontal lift (H41H), single-leaf swing (H44H), and double-leaf butterfly (H77H). These are widely used in heating and industrial applications.
Sixth, the regulating valve
Regulating valves, also referred to as throttle valves, are used to control the flow distribution in heating systems, especially in secondary networks. They resemble globe valves but have a different sealing mechanism.
Working Principle: The valve flap adjusts the flow area by moving up and down, similar to a thermos stopper. A scale on the stem indicates the flow setting, allowing for precise control.
Function: These valves help achieve thermal balance by regulating the flow of the medium between different parts of the system.
Although the straight-through model (T41H) is still used, it has limitations like high flow resistance and cannot be installed vertically. As a result, balancing valves (PH45F) have become more popular for better performance.
Seventh, the balancing valve
Balancing valves are an improved version of regulating valves. They feature a direct-flow channel and a more advanced sealing material, such as PTFE, to reduce flow resistance.
Advantages: They provide better sealing, a cut-off function, and superior flow control, especially in variable flow systems. They can be installed horizontally or vertically, making them versatile for various applications.
Self-operated Balancing Valve
Self-operated balancing valves, also known as flow control valves, use a spring and diaphragm mechanism inside the valve. When the flow increases, the imbalance force causes the valve to close slightly, reducing the flow back to the set value. This ensures a constant flow rate after the valve.
These valves are often installed at branch points in heating systems to automatically eliminate hydraulic imbalances, improving overall efficiency and economic operation. They are directional and must be installed correctly to function properly.
Ninth, the safety valve
Safety valves are critical for protecting equipment and systems from overpressure. When the pressure exceeds the set limit, the valve opens automatically to release excess pressure. Once the pressure returns to normal, it closes again, ensuring safe and stable operation.
Types: Safety valves can be classified based on their structure—spring-loaded, lever-type, or pulse-type. They can also be categorized by their opening ratio: micro-open (10% of the seat diameter) or full-open (20–30%).
Exhaust Type: Some safety valves discharge the medium through a pipeline (closed type), while others release it directly into the atmosphere (open type).
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